The UM6 and UM6-LT orientation sensors can represent orientation with quaternions, which avoid certain problems that can occur when using Euler angles. This application note from CH Robotics helps explain what quaternions are and how to use them.

This application note describes how to use the UM6 or the UM6-LT to estimate velocity and position (dead-reckoning using accelerometers). It also explains why this estimate will not be accurate enough for most applications.

The UM6 and UM6-LT orientation sensors each use a three-axis accelerometer, gyro, and magnetometer to estimate orientation. This application note explains in more detail the purpose of each sensor and the math involved in combining them.